Answer:
[tex] B = \frac{31.5}{5.25}= 6[/tex]
[tex] H = 18-6= 12[/tex]
So then Mark purchased 12 Hamburgers and 6 packages of buns
Step-by-step explanation:
For this case we can define the following notation:
B represent the number of packages buns
H represent the number of hamburgers
And from the information given we can set up the conditions into the following equations:
[tex] 6.75 H +1.50 B =90[/tex] (1) represent the total cost
[tex] H +B =18[/tex] (2) represent the total number of items
Solving H from equation (2) we got:
[tex] H = 18 -B [/tex] (3)
And replacing equation (3) into equation (1) we got:
[tex] 6.75 (18-B) +1.5 B =90[/tex]
And dsitributing the terms we have:
[tex] 121.5 -6.75 B +1.5 B =90[/tex]
And solving for B we got:
[tex] 121.5-90 = 5.25 B[/tex]
And dividing by 5.25 we got:
[tex] B = \frac{31.5}{5.25}= 6[/tex]
And replacing the value of B into equation (3) we got:
[tex] H = 18-6= 12[/tex]
So then Mark purchased 12 Hamburgers and 6 packages of buns